/**
 * @class Ext.form.Panel
 * @extends Ext.panel.Panel

FormPanel provides a standard container for forms. It is essentially a standard {@link Ext.panel.Panel} which
automatically creates a {@link Ext.form.Basic BasicForm} for managing any {@link Ext.form.field.Field}
objects that are added as descendants of the panel. It also includes conveniences for configuring and
working with the BasicForm and the collection of Fields.

__Layout__

By default, FormPanel is configured with `{@link Ext.layout.container.Anchor layout:'anchor'}` for
the layout of its immediate child items. This can be changed to any of the supported container layouts.
The layout of sub-containers is configured in {@link Ext.container.Container#layout the standard way}.

__BasicForm__

Although **not listed** as configuration options of FormPanel, the FormPanel class accepts all
of the config options supported by the {@link Ext.form.Basic} class, and will pass them along to
the internal BasicForm when it is created.

**Note**: If subclassing FormPanel, any configuration options for the BasicForm must be applied to
the `initialConfig` property of the FormPanel. Applying {@link Ext.form.Basic BasicForm}
configuration settings to `this` will *not* affect the BasicForm's configuration.

The following events fired by the BasicForm will be re-fired by the FormPanel and can therefore be
listened for on the FormPanel itself:

- {@link Ext.form.Basic#beforeaction beforeaction}
- {@link Ext.form.Basic#actionfailed actionfailed}
- {@link Ext.form.Basic#actioncomplete actioncomplete}
- {@link Ext.form.Basic#validitychange validitychange}
- {@link Ext.form.Basic#dirtychange dirtychange}

__Field Defaults__

The {@link #fieldDefaults} config option conveniently allows centralized configuration of default values
for all fields added as descendants of the FormPanel. Any config option recognized by implementations
of {@link Ext.form.Labelable} may be included in this object. See the {@link #fieldDefaults} documentation
for details of how the defaults are applied.

__Form Validation__

With the default configuration, form fields are validated on-the-fly while the user edits their values.
This can be controlled on a per-field basis (or via the {@link #fieldDefaults} config) with the field
config properties {@link Ext.form.field.Field#validateOnChange} and {@link Ext.form.field.Base#checkChangeEvents},
and the FormPanel's config properties {@link #pollForChanges} and {@link #pollInterval}.

Any component within the FormPanel can be configured with `formBind: true`. This will cause that
component to be automatically disabled when the form is invalid, and enabled when it is valid. This is most
commonly used for Button components to prevent submitting the form in an invalid state, but can be used on
any component type.

For more information on form validation see the following:

- {@link Ext.form.field.Field#validateOnChange}
- {@link #pollForChanges} and {@link #pollInterval}
- {@link Ext.form.field.VTypes}
- {@link Ext.form.Basic#doAction BasicForm.doAction clientValidation notes}

__Form Submission__

By default, Ext Forms are submitted through Ajax, using {@link Ext.form.action.Action}. See the documentation for
{@link Ext.form.Basic} for details.
{@img Ext.form.FormPanel/Ext.form.FormPanel.png Ext.form.FormPanel FormPanel component}
__Example usage:__

    Ext.create('Ext.form.Panel', {
        title: 'Simple Form',
        bodyPadding: 5,
        width: 350,
        
        // The form will submit an AJAX request to this URL when submitted
        url: 'save-form.php',
        
        // Fields will be arranged vertically, stretched to full width
        layout: 'anchor',
        defaults: {
            anchor: '100%'
        },
        
        // The fields
        defaultType: 'textfield',
        items: [{
            fieldLabel: 'First Name',
            name: 'first',
            allowBlank: false
        },{
            fieldLabel: 'Last Name',
            name: 'last',
            allowBlank: false
        }],
        
        // Reset and Submit buttons
        buttons: [{
            text: 'Reset',
            handler: function() {
                this.up('form').getForm().reset();
            }
        }, {
            text: 'Submit',
            formBind: true, //only enabled once the form is valid
            disabled: true,
            handler: function() {
                var form = this.up('form').getForm();
                if (form.isValid()) {
                    form.submit({
                        success: function(form, action) {
                           Ext.Msg.alert('Success', action.result.msg);
                        },
                        failure: function(form, action) {
                            Ext.Msg.alert('Failed', action.result.msg);
                        }
                    });
                }
            }
        }],
        renderTo: Ext.getBody()
    });

 * @constructor
 * @param {Object} config Configuration options
 * @xtype form
 *
 * @markdown
 * @docauthor Jason Johnston <jason@sencha.com>
 */
Ext.define('Ext.form.Panel', {
    extend:'Ext.panel.Panel',
    mixins: {
        fieldAncestor: 'Ext.form.FieldAncestor'
    },
    alias: 'widget.form',
    alternateClassName: ['Ext.FormPanel', 'Ext.form.FormPanel'],
    requires: ['Ext.form.Basic', 'Ext.util.TaskRunner'],

    /**
     * @cfg {Boolean} pollForChanges
     * If set to <tt>true</tt>, sets up an interval task (using the {@link #pollInterval}) in which the 
     * panel's fields are repeatedly checked for changes in their values. This is in addition to the normal detection
     * each field does on its own input element, and is not needed in most cases. It does, however, provide a
     * means to absolutely guarantee detection of all changes including some edge cases in some browsers which
     * do not fire native events. Defaults to <tt>false</tt>.
     */

    /**
     * @cfg {Number} pollInterval
     * Interval in milliseconds at which the form's fields are checked for value changes. Only used if
     * the {@link #pollForChanges} option is set to <tt>true</tt>. Defaults to 500 milliseconds.
     */

    /**
     * @cfg {String} layout The {@link Ext.container.Container#layout} for the form panel's immediate child items.
     * Defaults to <tt>'anchor'</tt>.
     */
    layout: 'anchor',

    ariaRole: 'form',

    initComponent: function() {
        var me = this;
        
        if (me.frame) {
            me.border = false;
        }
        
        me.initFieldAncestor();
        me.callParent();

        me.relayEvents(me.form, [
            'beforeaction',
            'actionfailed',
            'actioncomplete',
            'validitychange',
            'dirtychange'
        ]);

        // Start polling if configured
        if (me.pollForChanges) {
            me.startPolling(me.pollInterval || 500);
        }
    },

    initItems: function() {
        // Create the BasicForm
        var me = this;
        
        me.form = me.createForm();
        me.callParent();
        me.form.initialize();
    },

    /**
     * @private
     */
    createForm: function() {
        return Ext.create('Ext.form.Basic', this, Ext.applyIf({listeners: {}}, this.initialConfig));
    },

    /**
     * Provides access to the {@link Ext.form.Basic Form} which this Panel contains.
     * @return {Ext.form.Basic} The {@link Ext.form.Basic Form} which this Panel contains.
     */
    getForm: function() {
        return this.form;
    },
    
    /**
     * Loads an {@link Ext.data.Model} into this form (internally just calls {@link Ext.form.Basic#loadRecord})
     * See also {@link #trackResetOnLoad}.
     * @param {Ext.data.Model} record The record to load
     * @return {Ext.form.Basic} The Ext.form.Basic attached to this FormPanel
     */
    loadRecord: function(record) {
        return this.getForm().loadRecord(record);
    },
    
    /**
     * Returns the currently loaded Ext.data.Model instance if one was loaded via {@link #loadRecord}.
     * @return {Ext.data.Model} The loaded instance
     */
    getRecord: function() {
        return this.getForm().getRecord();
    },
    
    /**
     * Convenience function for fetching the current value of each field in the form. This is the same as calling
     * {@link Ext.form.Basic#getValues this.getForm().getValues()}
     * @return {Object} The current form field values, keyed by field name
     */
    getValues: function() {
        return this.getForm().getValues();
    },

    beforeDestroy: function() {
        this.stopPolling();
        this.form.destroy();
        this.callParent();
    },

    /**
     * This is a proxy for the underlying BasicForm's {@link Ext.form.Basic#load} call.
     * @param {Object} options The options to pass to the action (see {@link Ext.form.Basic#load} and
     * {@link Ext.form.Basic#doAction} for details)
     */
    load: function(options) {
        this.form.load(options);
    },

    /**
     * This is a proxy for the underlying BasicForm's {@link Ext.form.Basic#submit} call.
     * @param {Object} options The options to pass to the action (see {@link Ext.form.Basic#submit} and
     * {@link Ext.form.Basic#doAction} for details)
     */
    submit: function(options) {
        this.form.submit(options);
    },

    /*
     * Inherit docs, not using onDisable because it only gets fired
     * when the component is rendered.
     */
    disable: function(silent) {
        this.callParent(arguments);
        this.form.getFields().each(function(field) {
            field.disable();
        });
    },

    /*
     * Inherit docs, not using onEnable because it only gets fired
     * when the component is rendered.
     */
    enable: function(silent) {
        this.callParent(arguments);
        this.form.getFields().each(function(field) {
            field.enable();
        });
    },

    /**
     * Start an interval task to continuously poll all the fields in the form for changes in their
     * values. This is normally started automatically by setting the {@link #pollForChanges} config.
     * @param {Number} interval The interval in milliseconds at which the check should run.
     */
    startPolling: function(interval) {
        this.stopPolling();
        var task = Ext.create('Ext.util.TaskRunner', interval);
        task.start({
            interval: 0,
            run: this.checkChange,
            scope: this
        });
        this.pollTask = task;
    },

    /**
     * Stop a running interval task that was started by {@link #startPolling}.
     */
    stopPolling: function() {
        var task = this.pollTask;
        if (task) {
            task.stopAll();
            delete this.pollTask;
        }
    },

    /**
     * Forces each field within the form panel to 
     * {@link Ext.form.field.Field#checkChange check if its value has changed}.
     */
    checkChange: function() {
        this.form.getFields().each(function(field) {
            field.checkChange();
        });
    }
});
